The Sulfur K and L and Fluorine K X-Ray Emission and Absorption Spectra of Gaseous SF6

Abstract

With the exception of the sulfur L-absorption spectrum, measurements of all the soft x-ray spectra from gaseous SF6 in their respective threshold regions are reported. The valence emission x-ray spectra are interpreted in terms of a molecular orbital model of SF6 with the inclusion of sulfur d orbitals. The experimental emission profiles are in fair agreement with a calculated profile based on the assigned orbital ionization energies and molecular orbital theory. The sharp resonance structures in the absorption spectra are found to result from the potential barrier formed by the surrounding fluorine atoms and are consistent with the molecular orbital model. The identification of the absorption resonance structure in terms of transitions to ``virtual'' unoccupied electronic levels is substantiated by the observation of ``resonance radiation,'' i.e., x-ray emission in coincidence with the peak positions in the absorption region. The sulfur Kα spectrum is also presented and discussed. A notable feature in this spectrum is a weak peak on the low energy side of the Kα1,2 line, which is interpreted as a semi-Auger process.